This invention relates generally to pumps, and more particularly to centrifugal pumps used in medical applications.
It is known to use centrifugal pumps as cardiac assist devices, also known as left or right ventricular assist devices (“LVAD” or “RVAD”). In such applications, the pump is implanted in the patient along with a power source and a control system. Alternatively, the power source and control system may be located externally.
A centrifugal pump includes a rotating impeller contained in a housing which defines an inlet, and an annular chamber which surrounds the impeller, which is commonly referred to as a “volute”. Fluid flow enters the impeller near its center and exits from the periphery of the impeller. The flow exiting the impeller is collected in the volute and channeled to an outlet. Conventional centrifugal pump design places the volute section in axial alignment with the outside diameter of the impeller. This results in a very short fluid residence time in the impeller and volute, and a greater residence time of recirculating fluid in the more remote sections of the pump.
When used as a blood pump for a ventricular assist system, extended residence time of blood within a pump can cause thrombus (clot) formation, and hemolysis (damage of red blood cells), both of which are undesirable.